Originally developed for the G3, this stock adapter was modified for a Police agency to use with the MP5. However, there were concerns about using the SMG’s iron sights so the stick was lowered on the adapter an a quickly removable comb was introduced. With the comb in place, the eye is in line with an optical sight. With it removed the eye is on the iron sight plane.
This will only work on the MP5 and not the G3 due to the G3’s buffer.
Don’t see the point compared to a regular M4-stock adapter with a riser if there is an optik? It is not like the MP5 has noticeable recoil? Looks like a luxury solution instead of the cheaper buffer tube adapter.